Orbital operations are expensive and complex. One reason for this is that all the goods and supply needed for an operation needs to be supplied from somewhere else, either another orbit or from the ground. Another reason is that, in orbit, everything is in motion, including space objects and debris from prior human operations. Yet another reason is that orbital environments are harsh, with excessive radiation and vacuum present.
With everything in orbit being in motion, consideration needs to be given to rendezvous and changes in orbit. Some objects, such as space probes and some satellites might not have any propulsion systems and are left to the orbits where they are placed. Of course, some such devices might change orbits over time due to drag or other collisions or other perturbations. Other objects have their own propulsion systems, allowing them to make minor adjustments, such as needed to stay in a given orbit, or major adjustments that allow them to change orbits and/or change positions relative to other objects. For example, the Space Shuttle has a propulsion system that allows it to maneuver around other objects in orbit and change orbits (including the extreme case of a change in orbit from an orbital position above the Earth to a ground position on Earth).
One scheme for performing operations in orbit is the use of a space platform (also referred to herein as a “platform”). A space platform is launched and placed in an orbit or is constructed in orbit from parts launched from Earth, or possibly from components and/or construction materials from nonterrestrial sources. Once in place, the space platform serves as a base for the operations. Such operations might include space exploration, experimentation, satellite maintenance or construction, or other operations suited for performance in orbit. One example of a space platform is the International Space Station (ISS) being put into operation by a consortium of countries. Other examples include the Mir and Skylab-type space stations.
In some cases, space vehicles or space-bound objects might be considered space platforms, either permanently or temporarily. For example, while in orbit, the U.S. Space Shuttle serves as a temporary space platform for satellite recovery operations and research. In addition to government-funded platforms, several private companies are planning to develop and put into operation commercial space platforms. In some cases, a satellite or other orbiting object could be considered a platform, but typically a space platform provides for human occupation.
As part of the construction, repair and/or operation of a space platform, the space platform normally requires initial supply and resupply (generically referred to herein as “supply”). In some cases, such as where the platform is a temporary space platform, the mission of the platform might be fully supplied at the outset for a self-sufficient mission, but more typically, a space platform needs supply. Permanent space platforms, such as the ISS, typically require significant logistics for supply. In fact, as the ISS becomes fully operational, the amount of goods required to service the ISS might well exceed the capacity of current baselined ISS service vehicles such as the Space Shuttle.
As used herein, the term “supply” can refer to the provision of multiple kinds of goods to a platform. These includes logistical supplies needed by the platform, such as food, water, air, propellant or other consumables, or equipment to provide additional capabilities such as power or on-board computing for experiments, or platform housekeeping functions. Supply can also mean provision of additional pressurized or unpressurized storage capability. In addition, supply can also include materials needed for purposes beyond the platform, such as propellant for or parts of other spacecraft that would be assembled and/or serviced at or beyond the platform itself. In some arrangements, supply can also include crew, i.e., where a supply mission includes the transport of fresh crew as replacements for crew already at the space platform.
Much literature and prior art exists on the subject of supply.
Some actually implemented systems include canisters for carrying cargo into space, such as the Long Exposure Duration Facility (LDEF), launched Apr. 7, 1984 on Space Shuttle mission STS 41-C, and returned to Earth on Jan. 20, 1990 on Space Shuttle mission STS-32. However, LDEF remained in its initial orbit until it was picked up by the Space Shuttle and was returned to Earth, and was not transferred to another orbit to deliver cargo to a space platform.
U.S. Pat. Nos. 4,834,324 and 5,217,187 show a space transportation system comprising modular units that could include a payload canister. However, that disclosure only addressed the placement of the payload canister into an initial orbit, where it presumably would have remained unless it moved to another orbit with its own propulsive capability, if available.
U.S. Pat. No. 4,471,926 describes a method for a launch vehicle upper stage (space transfer vehicle), for use in connection with a satellite to be moved from a launch vehicle's orbit into another orbit, of segregating the main propulsive capability of the satellite from the satellite's payload functions by placing the function with the space transfer vehicle. However, that satellite was expensive and heavy as it carried its own housekeeping functions and subsystems, such as attitude control, so that it could function as an independent vehicle once the transfer vehicle had detached from the satellite.
U.S. Pat. Nos. 5,152,482 and 5,271,582 show the use of a standardized spacecraft bus for segregating various subsystem functions, such as main propulsion and attitude control, from pre-integrated payloads.
U.S. Pat. No. 5,429,328 shows a spacecraft payload exchange system that employs a servicing vehicle, a plurality of canisters and the exchange of material-containing canisters from the servicing vehicle to a space platform and vice versa using a docking method. However, the initial transfer of canisters occurs directly at the space platform, with the servicing vehicle using the direct transportation method from the launch vehicle to the space platform, which does not avoid the problems of direct transportation.
U.S. Pat. No. 4,880,187 shows the transfer of a spacecraft from one orbit to another.
U.S. Pat. No. 4,964,596 shows a spacecraft payload module with a fitting at one end that is assembled on-orbit with a bus module using the Space Shuttle. However, the payload module is assembled with the bus module using a robotic arm which generally requires operator assistance and its stabilizing and propulsive ability is limited.
U.S. Pat. Nos. 6,149,104, 6,193,193 and 6,322,023 show provision of space platform rendezvous functions for a cargo module using a separate space tug. However, these methods all use the direct transportation method from the launch vehicle to the space platform, which is disadvantageous for the reasons described herein.
Furthermore, Waltz, Donald M., On-Orbit Servicing of Space Systems, (Krieger Publishing) illustrates a launch of an unpressurized cargo carrier carrying supplies to a space platform using a space tug with a spin-stabilized upper stage.
J Collins, John T., et. al., Small Orbit Transfer Vehicle (OTV) for On-Orbit Satellite Servicing and Resupply, 15th Annual AIAA/USU Conference on Small Satellites, Aug. 13-16, 2001, specifically describes using a space tug to retrieve a payload canister that has been placed into orbit by a launch vehicle upper stage, and transporting that canister to a space platform (specifically ISS). However, there the space tug is attached to the space platform by a robotic arm, limiting its usefulness and requiring human intervention. An additional use of the robotic arm might be required to then berth the payload canister to the space platform.
Intermodal transport of containers in a terrestrial environment is common. For example, consumer goods transported in part by ship are often packed into standardized containers, placed on ships, offloaded at a destination port onto trains, and then offloaded onto trucks for delivery to their final destination. U.S. Pat. Nos. 3,027,025, 3,456,829 and 3,966,075 described such intermodal terrestrial transport. Of course, terrestrial transport, intermodal or otherwise, is much simpler that space transport.
In the typical space platform supply process, elements of which are described in the above references, the supply is part of a payload attached to a launch vehicle that is launched from Earth into the launch vehicle's orbit. Of course, what remains in orbit might only a launch vehicle element, such as the upper stage of the launch vehicle, with the payload attached thereto. The launch vehicle, or what remains of it, includes a propulsion module, means or section and a cargo module, means or section, integrated as a unit. The Russian Soyuz launch vehicle and Progress spacecraft are an example of such an integrated unit.
The integrated unit approaches the space platform and attaches to the space platform for transfer of the cargo into the platform. The attachment could be via a docking maneuver, via berthing of the entire integrated unit to the space platform using a robotic arm, via attachment of the cargo module of the integrated unit to the space platform using a robotic arm, via attachment of the cargo module to the space platform by crew performing extra-vehicular activity (EVA), or similar approaches.
The Space Shuttle/SpaceHab/Multi-Purpose Logistics Module (MPLM) system is an example of one approach. In that system, the entire launch vehicle element, with the cargo module attached, directly travels to and docks with the space platform. The cargo can be stored within the launch vehicle (i.e., the Space Shuttle) and transferred by its crew into the space platform after docking, stored in a cargo module inside the Space Shuttle (e.g., a SpaceHab or SpaceLab module) or stored in a cargo module that is transferred from the Space Shuttle payload bay and berthed using a robotic arm to a port at the space platform where the cargo can be later transferred by the crew. In the history of space platforms, actual implementation of logistics supply has been via this direct transportation method using an integrated propulsion/cargo unit.
Plans to augment the ISS supply chain currently call for development of new vehicles that also use this direct transport method. Examples of such plans include the European Ariane 5 launch vehicle with an “Automated Transfer Vehicle” using direct transport and docking, and the Japanese H2A launch vehicle with a “H2 Transfer Vehicle” using direct transport and berthing, and a variety of other concepts now being developed by U.S. companies. These new developments will be very costly, with investments required in excess of $100 million for each project.
Clearly, there is a need for inexpensive supply as it is a significant cost of many missions.